1. Field of the Invention
The present invention relates to a fuel processor, and more particular to a preferential oxidation reactor integrated with a heat exchanger capable of effectively removing carbon monoxide (CO) contained in reformed gas.
2. Discussion of Related Art
A fuel processor is referred to as a process and a system that produces hydrogen from fuel. The fuel processor is constituted by an apparatus that reforms fuel to produce reformed gas and an apparatus that removes sulfur and/or carbon monoxide contained in reformed gas. The hydrogen produced by the fuel processor has been used in a power generation system such as a fuel cell, etc.
Since the fuel cell is a pollution-free power supply apparatus, it has been spotlighted as one of next-generation clean energy power generation systems. The power generation system using the fuel cell can be utilized as a self generator of a large building, a power supply of an electric vehicle, a portable power supply, and the like, and is advantageous of being capable of using various fuels such as natural gas, methanol, petroleum, liquefied petroleum gas (LPG), dimethyl ether (DME), coal, waste gas, and the like. The fuel cell is essentially operated by the same principle, and can be sorted into a phosphoric acid fuel cell, an alkaline fuel cell, a polymer electrolyte membrane fuel cell, a direct methanol fuel cell, and a solid oxide fuel cell depending on its internal electrolyte.
Among others, since the polymer electrolyte membrane fuel cell (PEMFC) uses a polymer membrane as electrolyte, it has no risk of corrosion or evaporation and can obtain a high current density per unit area. Moreover, since the polymer electrolyte membrane fuel cell is very high in output characteristics and low in operating temperature over other kinds of fuel cells, it has actively been developed as a portable power supply for supplying power to a vehicle, a distributed power supply for supplying power to a house or a public building, etc., and a small power supply for supplying power to a portable electronic equipment, etc.
The polymer electrolyte membrane fuel cell produces electric energy by an electro-chemical reaction of hydrogen supplied to its anode side and oxygen supplied to its cathode side. As hydrogen, there has been used pure hydrogen or a hydrogen storage alloy which generates hydrogen gas, or hydrogen in reformed gas obtained from fossil fuels. As oxygen, there has been used pure oxygen or oxygen contained in air. However, in case of using the pure hydrogen or the hydrogen storage alloy, it is disadvantageous of involving a high cost due to the difficulties of production, storage, and transportation. Therefore, as hydrogen fuel for a fuel cell, hydrogen-rich reformed gas obtainable from a fuel reformer has usually bee used.
As the fuel reformer, there has been a steam reforming (SR) reactor that produces hydrogen-rich reformed gas by the reaction of fuel and steam, a partial oxidation (POX) reactor that produces hydrogen-rich reformed gas by oxidizing fuel, and a reactor that combines the steam reforming reaction and the partial oxidation reaction. And, as a carbon monoxide reducer which removes carbon monoxide contained in the reformed gas, there has been a water gas shift reactor or a preferential oxidation (PROX) reactor.
In general, the PROX reactor mixes air with the reformed gas and then removes carbon monoxide from the reformed gas by using a catalyst having high carbon monoxide selectivity. In order to make the selectivity and rate of the oxidation reaction better, the temperature of the reactor is required to be maintained in the temperature range of about 130 to 250° C. However, since the preferential oxidation reaction is an exothermic reaction accompanied by a large heat generation, it is very difficult to maintain the temperature range. Further, since the PROX reactor may easily generate the temperature difference in the flow direction of the reformed gas, it is very difficult to maintain the uniform reaction temperature in the entire reactor. Therefore, it is difficult to control the PROX reactor in order to generate the uniform oxidation reaction in the PROX reactor. As such, since in the PROX reactor sensitive to the temperature, its performance is considerably varied according to the temperature range, it is necessary to suppress the temperature variation of the reactor and maintain the temperature in the constant range.
Also, when a high temperature of hot spots occur, the activation of catalysts located at the hot spots is rapidly reduced and the hot spots are gradually diffused so that the phenomenon considerably reducing the activation of the catalysts in the reactor occurs. Therefore, it has been demanded a scheme capable of reducing a problem of that the reaction gas is drifted in the catalyst layer, so as not to generate the hot spots.